JP6762266B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire in which a plurality of ribbed land portions are formed by a plurality of circumferential grooves, and particularly to a tread structure.

Pneumatic tires with a plurality of circumferential grooves on the tread and a rib pattern are designed to promote drainage by the circumferential grooves even on a wet road surface to ensure frictional force (wet grip performance).
However, if the rib-shaped land portion partitioned by the circumferential groove touches the ground and there is elastic deformation such as compression deformation or collapse of the rib-shaped land portion, the tread portion generates heat due to the energy loss due to the hysteresis loss generated by the deformation. However, rolling resistance tends to increase.

Therefore, when the rib-shaped land portions are projected from the adjacent rib-shaped land portions across the circumferential groove toward each other and the rib-shaped land portions touch the ground, the opposing rib-shaped land portions come into contact with each other and mutually. An example has been proposed in which the rib-shaped land portion is maintained in rigidity and deformation is suppressed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-88288

The circumferential groove extending in the tread circumferential direction of the pneumatic tire according to Patent Document 1 is formed at an intermediate depth position of the groove between the tread tread surface and the groove bottom, and the rib-shaped land portion touches the ground. When this is done, the intermediate depths of the opposite groove wall surfaces of the rib-shaped land portion bulge in the direction of each other, and the opposing ridges come into contact with each other to suppress the deformation and suppress the increase in rolling resistance. Since the outer groove space is formed on the outer peripheral side of the opposing ridges, the drainage property can be maintained and the wet grip performance can be ensured by the outer groove space.

In the pneumatic tire disclosed in Patent Document 1, four circumferential grooves are formed, and all four circumferential grooves project from adjacent land portions with the circumferential grooves in between toward each other. A protrusion (protruding portion) is provided, and the protrusion in any circumferential groove is formed at an intermediate depth position of the groove between the tread tread and the bottom of the groove.

In a pneumatic tire, the running growth in which the tire outer diameter gradually increases with running is shown in FIG. 6 when the tire is new because the outer diameter in the outermost outermost circumferential groove in the tire width direction grows fastest. Such a footprint P is formed.
The footprint P shown in FIG. 6 is a footprint of a pneumatic tire according to an embodiment of the present invention described later, and the footprint P will be described below using the footprint P.

The pneumatic tire forming this footprint P has one equatorial circumferential groove on the tire equatorial line Lc, two outermost circumferential grooves located on the outermost side in the tire width direction, and a tire from the outermost circumferential groove. This is an example of having a total of five circumferential grooves, two inner adjacent circumferential grooves located adjacent to each other in the width direction (see FIGS. 1 and 2), and the footprint P is shown in FIG. Therefore, one equatorial circumferential groove trace Mc, two outermost circumferential groove traces Ms, and two inner adjacent circumferential groove traces Mn are printed.

As shown in FIG. 6, in the footprint P when the tire is new, the front-rear length of the equatorial circumferential groove trace Mc and the traces of both outer parts of the tire is the longest, and the front-rear length of the outermost circumferential groove trace Ms between them is the longest. The shortest, the front edge Ef and the trailing edge Er of the footprint P are wavy and have a butterfly shape as a whole.

When the vehicle travels on a wet road surface, the front edge of the tire contact patch (corresponding to the front edge Ef of the footprint) acts to drive water forward, and the outermost circumferential groove trace of the wavy front edge Ef. Water is most likely to collect in the left and right recesses Vs and Vs where Ms is located, and also easily in the front Vc of the central convex portion where the equatorial circumferential groove trace Mc is located.

Therefore, while the outermost circumferential groove is required to have high drainage property, the inner adjacent circumferential groove is not required to have high drainage property, but the pneumatic tire according to Patent Document 1 is required to have high drainage property. In addition, a protrusion is formed at the intermediate depth position of the groove between the tread tread and the bottom of the groove, and an outer groove space is formed on the outer peripheral side of the protrusion with a sufficient volume to ensure high drainage. There is.
Therefore, it is suitable for the outermost circumferential groove that requires high drainage, but the inner adjacent circumferential groove that does not require high drainage has a structure having more drainage than necessary.

The present invention has been made in view of this point, and an object of the present invention is to have appropriate drainage property according to the position of the circumferential groove in the tire width direction while suppressing an increase in rolling resistance, and to make a ground contact. The point is to provide pneumatic tires that can improve wet grip performance by expanding the area.

In order to achieve the above object, the pneumatic tire according to the present invention
In a pneumatic tire in which a plurality of rib-shaped land portions are formed by at least four circumferential grooves extending in the circumferential direction of the tread.
Protruding portions protruding in the direction of each other from both side wall surfaces of the rib-shaped land portions adjacent to each other across the circumferential groove are formed so as to extend in the circumferential direction of the tread.
The opposing ridges have a gap between them and the bottom of the groove, and the tip surfaces of the ridges facing each other have a gap in contact with each other due to elastic deformation of the rib-shaped land portion that touches the ground when the tire touches the ground. Arranged,
The ridge portion in the inner adjacent circumferential groove located adjacent to the innermost in the tire width direction from the outermost circumferential groove portion located on the outermost side in the tire width direction of the circumferential groove is the outermost circumferential groove. It is characterized in that it is formed at a shallower position closer to the tread tread of the groove between the tread tread and the groove bottom than the ridge portion.

According to this configuration, the ridge portion in the outermost circumferential groove located on the outermost side in the tire width direction of the circumferential groove is formed at the depth position of the groove between the tread tread surface and the groove bottom. When the rib-shaped land portion touches the ground, the opposing ridges come into contact with each other and support each other, suppressing the deformation of the rib-shaped land portion and suppressing the increase in rolling resistance, and the outer circumference of the rib-shaped land portion. The outer groove space is formed on the side with a sufficient volume to provide high drainage, and the water accumulated in the recess in front of the outermost circumferential groove trace can be efficiently discharged, and the wet grip performance can be ensured high.

On the other hand, the ridge portion in the inner adjacent circumferential groove located adjacent to the inner side in the tire width direction from the outermost circumferential groove is the groove between the tread tread and the groove bottom from the ridge portion in the outermost circumferential groove. It is formed at a shallow position near the tread tread, and when the ribbed land part touches the ground, the opposing ridges come into contact with each other and support each other, suppressing an increase in rolling resistance and the ridges at a shallow position. Although it is formed and the drainage property is not high, it is difficult for water to collect in front of the groove trace in the inner adjacent circumferential direction, so that the necessary drainage property is secured and the ridge portion formed at a shallow position near the tread tread is formed. There is a high possibility of grounding, and the wet grip performance can be improved by expanding the grounding area.
That is, in both the outermost circumferential groove and the inner adjacent circumferential groove, the increase in rolling resistance is suppressed, and the outermost circumferential groove mainly drains water efficiently to improve the wet grip performance as a whole. Can be done.

In the above configuration
The ridge portion in the outermost circumferential groove is located at an intermediate depth of the groove between the tread tread and the groove bottom, and is on the groove bottom side of the inner peripheral surface of the ridge portion in the inner adjacent circumferential groove. It may be formed at a deep position in the groove of.

According to this configuration, the ridge portion in the outermost circumferential groove is located at the intermediate depth of the groove between the tread tread and the groove bottom, and is a groove from the inner peripheral surface of the ridge portion in the inner adjacent circumferential groove. Since it is formed at the deep position of the groove on the bottom side, the wear on the tread surface reaches the ridge formed at the shallow position of the inner adjacent circumferential groove, and until the ridge is lost, the inner neighbor is formed. The circumferential groove is closed by the same ridges that are in contact with each other, but in the outermost circumferential groove, the outer groove space still remains on the outer peripheral side of the ridge, drainage can be maintained, and the inner adjacent circumferential groove can be maintained. Since the groove space opens in the inner adjacent circumferential groove after the ridge portion is lost, drainage is secured even if the outermost circumferential groove is blocked by the ridge portion.
That is, drainage is ensured by at least one of the outermost circumferential groove and the inner adjacent circumferential groove, and the wet grip performance can be maintained from the time when the tire is new until it is completely worn.
Here, the intermediate depth of the groove between the tread tread where the ridge is located and the groove bottom is the depth at which the distance from the tread tread to the ridge and the distance from the ridge to the groove bottom are approximately equal. That is.

In addition, until the ridges of the inner and adjacent circumferential grooves are substantially lost due to wear, the rigidity of the rib-shaped land portion is ensured by the outermost ridges and the inner and adjacent circumferential grooves, and the rolling resistance is reduced. The increase can be suppressed.
After the ridges of the inner adjacent circumferential groove are lost, the rib-shaped land portions on both sides of the inner adjacent circumferential groove have a smaller protrusion length (height) from the groove bottom. The rigidity of the land portion is not significantly reduced, and the increase in rolling resistance is moderately suppressed.

In the above configuration
A plurality of the ridge portions in the inner adjacent circumferential groove may be formed at intervals in the tread circumferential direction.

According to this configuration, a plurality of ridges in the inner adjacent circumferential groove are formed at intervals in the tread circumferential direction, so that the ridges formed in the shallow groove in the inner adjacent circumferential groove are formed. , The volume of the outer groove space on the outer peripheral side of the ridge is small and high drainage cannot be expected. However, the drainage can be improved by forming multiple ridges with intervals in the circumferential direction of the tread. , Drain the water in front of the inner adjacent circumferential groove trace to reduce the burden of drainage by the outermost circumferential groove by suppressing the flow of water toward the outermost circumferential groove, and drainage is effective. It is possible to improve the wet grip performance as a whole.

In the above configuration
The ridge portion in the outermost circumferential groove may be formed continuously in the tread circumferential direction.

According to this configuration, the ridges in the outermost circumferential groove are continuously formed in the tread circumferential direction, so that when the rib-shaped land portion touches the ground, the ridges facing each other are continuously in contact with each other. Since they support each other firmly, deformation of the ribbed land portion can be suppressed as much as possible, and an increase in rolling resistance can be reliably suppressed.

In the above configuration
The ridge portion of the equator circumferential groove located at the center of the tire width direction of the circumferential groove is formed at an intermediate depth position of the groove between the tread tread and the groove bottom. You may.

According to this configuration, the ridge portion in the equatorial circumferential groove located on the tire equatorial line is formed at the intermediate depth position of the groove between the tread tread and the groove bottom, so that the rib-shaped land portion touches the ground. When this happens, the opposing ridges come into contact with each other and support each other, suppressing the deformation of the ribbed land portion and suppressing the increase in rolling resistance, and there is sufficient outer groove space on the outer peripheral side of the ridges. It has a large volume and high drainage, efficiently drains the water that collects in front of the equatorial gutter trace, and suppresses the flow of water toward the inner adjacent gutter and the outermost gutter. , The burden of drainage in the outermost circumferential groove can be reduced, the drainage can be effectively shared, and the wet grip performance as a whole over the entire tire width direction can be improved.

In the above configuration
The ridge portion in the equatorial circumferential groove may be formed continuously in the tread circumferential direction.

According to this configuration, the ridges in the equatorial circumferential groove are continuously formed in the tread circumferential direction, so that when the ribbed land is in contact with the ground, the ridges facing each other are in continuous contact with each other. Since they firmly support each other, deformation of the ribbed land portion can be suppressed as much as possible, and an increase in rolling resistance can be reliably suppressed.

In the above configuration
The ridge portion in the equatorial circumferential groove may be formed at a position deep in the groove on the groove bottom side of the inner peripheral surface of the ridge portion in the inner adjacent circumferential groove.

According to this configuration, the ridge portion in the equatorial circumferential groove is formed at a position deeper in the groove bottom side than the inner peripheral surface of the ridge portion in the inner adjacent circumferential groove, so that the tread surface is worn. Until the ridges formed at the shallow position of the inner adjacent circumferential groove are reached and the ridges are lost, the inner adjacent circumferential grooves are blocked by the ridges in contact with each other, but the equatorial circumference. In the directional groove, the outer groove space still remains on the outer peripheral side of the ridge, drainage can be maintained, and after the ridge of the inner adjacent circumferential groove is lost, the groove space remains in the inner adjacent circumferential groove. Since it opens, drainage is ensured even if the equatorial gutter is blocked by the ridge.
That is, drainage is ensured by at least one of the equatorial circumferential groove and the inner adjacent circumferential groove, and the wet grip performance can be maintained from the time when the tire is new until it is completely worn.

In addition, the rigidity of the ribbed land portion is ensured by each of the ridges of the equatorial circumferential groove and the inner adjacent circumferential groove until the ridges of the inner adjacent circumferential groove are substantially lost due to wear, and rolling resistance increases. Can be suppressed.
After the ridges of the inner adjacent circumferential groove are lost, the rib-shaped land portions on both sides of the inner adjacent circumferential groove have a smaller protrusion length (height) from the groove bottom. The rigidity of the land portion is not significantly reduced, and the increase in rolling resistance is moderately suppressed.

In the above configuration
The belt layer embedded in the tread portion where the circumferential groove is formed is composed of a plurality of inclined belts in which the cord is oriented in an inclined direction with respect to the tire equatorial line.
The outermost circumferential groove may be located within the width of the belt layer in the tire width direction.

According to this configuration, the belt layer embedded in the tread portion where the circumferential groove is formed is composed of a plurality of inclined belts whose cords are oriented in the direction inclined with respect to the tire equatorial line, and is formed by stacking a plurality of inclined belts. Since the directional groove is located within the width of the belt layer in the tire width direction, the footprint when the tire is new is made to have a typical butterfly shape so that the footprint becomes rectangular during running growth.

In a pneumatic tire with a typical butterfly-shaped footprint when the tire is new, the ridge of the inner adjacent circumferential groove is from the tread tread to the groove bottom rather than the ridge of the outermost circumferential groove. The configuration formed at a shallow position near the tread tread of the groove between them is the most suitable, and it efficiently discharges the water accumulated in front of the outermost circumferential groove trace while suppressing the increase in rolling resistance, and was once the inner adjacent circumference. The effect of improving the wet grip performance can be more remarkably exhibited by expanding the contact area due to the ridge portion in the directional groove.

In the present invention, the ridge portion of the inner adjacent circumferential groove is formed at a position shallower than the ridge portion of the outermost circumferential groove near the tread tread of the groove from the tread tread to the bottom of the groove, so that rolling resistance is formed. It is possible to improve the wet grip performance by efficiently discharging the water accumulated in front of the outermost circumferential groove trace while suppressing the increase of the tire, and to improve the grip performance by expanding the ground contact area in the inner adjacent circumferential groove.

It is a cross-sectional view in the width direction of the pneumatic tire of the embodiment according to the present invention (cross-sectional view taken along the line II of FIG. It is a partial plan view of the pneumatic tire in the circumferential direction. It is an enlarged sectional view in the width direction of the outermost circumferential groove. It is an enlarged sectional view in the width direction of the groove in the inner adjacent circumferential direction. It is an enlarged cross-sectional view in the width direction of the groove in the equatorial circumferential direction. It is a figure which shows the footprint of the same pneumatic tire.

Hereinafter, the pneumatic tire 1 according to the embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a partial cross-sectional view in the width direction of the pneumatic tire 1, and FIG. 2 is a partial plan view in the circumferential direction of the pneumatic tire.

With reference to FIG. 1, in the pneumatic tire 1, the carcass 2 which is a rubber coating layer of a ply extending in the radial direction is formed in a toroidal shape between a pair of bead cores (not shown), and the crown portion of the carcass 2 is formed. A tread 4 is formed on the outer side of the tire in the radial direction via a plurality of belt layers 3.
Although the carcass 2 shown in FIG. 1 is composed of two layers, it may be composed of one layer.

The belt layer 3 is composed of a plurality of inclined belts whose cords are oriented in an inclined direction with respect to the tire equatorial line Lc.
The tread 4 is composed of a rib pattern in which six rib-shaped land portions (parts with scattered dots in FIG. 1) 6 are formed by five circumferential grooves 5 extending in the circumferential direction of the tread. Has been done.

One equatorial circumferential groove 5C is formed at the center of the tire equatorial line Lc in the tread width direction, and two outermost circumferential grooves 5S are formed at the outermost left and right sides in the tire width direction. Two inner adjacent circumferential grooves 5N are formed so as to be adjacent to each other on the inner side in the tire width direction from the circumferential groove 5S.
As shown in FIG. 1, the outermost circumferential groove 5S is located within the width W of the belt layer 3 in the tire width direction.

In the outermost circumferential groove 5S, ridges 7S and 7S protruding in the direction of each other from both side wall surfaces of the adjacent rib-shaped land portions 6 and 6 facing each other extend in the tread circumferential direction. It is formed.
The ridge portion 7S is formed in an annular shape continuously in the circumferential direction of the tread.

There is a gap between the tip surfaces of the opposing ridges 7S and 7S facing each other, and the gap is formed by the elastic deformation of the ribbed ridges 6 and 6 that touched the ground when the tire touched down. The interval is set so that the tip surfaces of the 7S come into close contact with each other.

The ridge portion 7S in the outermost circumferential groove 5S is formed at an intermediate depth position of the groove between the tread tread surface 6f and the groove bottom 8s.
With reference to FIG. 3, the ridge portion 7S in the outermost circumferential groove 5S has a depth of Dsa from the tread tread surface 6f to the outer peripheral surface 7sa of the ridge portion 7S, and the inner peripheral surface 7sb of the ridge portion 7S. The depth to is Dsb, and it is formed at an intermediate depth position between the depths Dsa and Dsb.

Therefore, the outermost peripheral groove 5S has the outer groove space 5So on the outer peripheral side of the outer peripheral surfaces 7sa and 7sa of the ridges 7S and 7S and the inner circumference of the ridges 7S and 7S by the opposing ridges 7S and 7S. It is divided into an inner groove space 5Si on the inner peripheral side of the surfaces 7sb and 7sb.
The outer groove space 5So has a volume substantially equal to that of the inner groove space 5Si, and has a sufficient volume for obtaining good drainage.

Located adjacent to each other in the tire width direction from the outermost circumferential groove 5S, the inner adjacent circumferential groove 5N faces each other from both side wall surfaces of adjacent ribbed land portions 6 and 6 facing each other. The protruding protrusions 7N and 7N are formed so as to extend in the circumferential direction of the tread.
A plurality of ridge portions 7N are formed at intervals in the tread circumferential direction, and each ridge portion 7N is formed in an arc shape.

There is a gap between the tip surfaces of the opposing ridges 7N and 7N facing each other, and the gap is the ridge 7N, which faces each other due to the elastic deformation of the ribbed land parts 6 and 6 that touched the ground when the tire touched down. The interval is set so that the tip surfaces of 7N come into close contact with each other.

The ridge portion 7N in the inner adjacent circumferential groove 5N is formed at a position shallower than the ridge portion 7S in the outermost circumferential groove 5S near the tread tread 6f of the groove between the tread tread 6f and the groove bottom 8s. There is.
With reference to FIG. 4, the ridge portion 7N in the inner adjacent circumferential groove 5N is a Dna having an extremely shallow depth from the tread tread 6f to the outer peripheral surface 7na of the ridge portion 7N, and is the inner circumference of the ridge portion 7N. The depth to the surface 7nb is Dnb, and the groove is formed at a shallow position closer to the tread tread 6f of the groove between the depths Dna and Dnb.

Therefore, the inner peripheral groove 5N has the outer groove space 5No on the outer peripheral side of the outer peripheral surfaces 7na and 7na of the ridges 7N and 7N and the inner circumference of the ridges 7N and 7N due to the opposing ridges 7N and 7N. It is divided into an inner groove space 5Ni on the inner peripheral side of the surfaces 7nb and 7nb.
Since the depth Dna up to the outer peripheral surfaces 7na and 7na of the ridges 7N and 7N is shallow, the outer groove space 5No occupies a small volume.

In the ridge portion 7C in the equatorial circumferential groove 5C, the ridge portions 7C and 7C protruding from both of the side wall surfaces of the adjacent rib-shaped land portions 6 and 6 facing each other toward each other are formed in the tread circumferential direction. It is formed by extending to.
The ridge portion 7C is formed in an annular shape continuously in the circumferential direction of the tread.

There is a gap between the tip surfaces of the opposing ridges 7C and 7C facing each other, and the gap is the ridges 7C, which face each other due to the elastic deformation of the ribbed land parts 6 and 6 that touched the ground when the tire touched down. The interval is set so that the tip surfaces of 7C come into close contact with each other.

With reference to FIG. 5, the ridge portion 7C in the equatorial circumferential groove 5C is the intermediate depth of the groove between the tread tread 6f and the groove bottom 8c, similarly to the ridge portion 7S in the outermost circumferential groove 5S. It is formed in the position.
The depth of the ridge portion 7C in the equatorial circumferential groove 5C is Dca from the tread tread 6f to the outer peripheral surface 7ca of the ridge portion 7C, and the depth of the ridge portion 7C to the inner peripheral surface 7cb is Dcb. , Depth is formed at an intermediate depth position between Dca and Dcb.

Therefore, the equatorial groove 5C has the outer groove space 5Co on the outer peripheral side of the outer peripheral surfaces 7ca and 7ca of the ridges 7C and 7C and the inner peripheral surface of the ridges 7C and 7C due to the opposing ridges 7C and 7C. It is divided into an inner groove space 5Ci on the inner peripheral side of 7cb and 7cb.
The outer groove space 5Co has a volume substantially equal to that of the inner groove space 5Ci, and has a sufficient volume for obtaining good drainage.

The ridge portion 7S in the outermost circumferential groove 5S is located at the intermediate depth of the groove between the tread tread 6f and the groove bottom 8s, and is from the inner peripheral surface 7nb of the ridge portion 7N in the inner adjacent circumferential groove 5N. It is formed at a deep position of the groove on the groove bottom 8s side.
That is, there is the following relationship.
Dsa (depth of outer peripheral surface 7sa of ridge 7S)> Dnb (depth of inner peripheral surface 7nb of ridge 7N)

Similarly, the ridge portion 7C in the equatorial circumferential groove 5C is formed at a position deep in the groove on the groove bottom 8c side of the inner peripheral surface 7nb of the ridge portion 7N in the inner adjacent circumferential groove 5N.
That is, there is the following relationship.
Dca (depth of outer peripheral surface 7ca of ridge 7C)> Dnb (depth of inner peripheral surface 7nb of ridge 7N)

As shown in FIG. 1, in the pneumatic tire 1 according to the present embodiment, the cord of the belt layer 3 provided around the outer side of the crown portion of the carcass 2 in the tire radial direction is inclined with respect to the tire equatorial line Lc. It is composed of a plurality of inclined belts oriented in the direction of the tire, and is located on the outermost side of the five circumferential grooves 5 extending in the tread circumferential direction of the tread 4, which is located on the outermost side in the tire width direction. The grooves 5S and 5S are located within the width W of the belt layer 3 in the tire width direction.

Since the pneumatic tire 1 has such a structure, the footprint P when the tire is new has a typical butterfly shape as shown in FIG. 6 so that the footprint becomes rectangular during running growth.

The footprint P includes an equatorial circumferential groove trace Mc corresponding to the equatorial circumferential groove 5C on the tire equatorial line Lc of the tread 4 of the pneumatic tire 1, and an outermost circumferential groove 5S located on the outermost side in the tire width direction. , 5S, outermost circumferential groove traces Ms, Ms, inner adjacent circumferential groove traces Mn corresponding to inner adjacent circumferential grooves 5N, 5N located adjacent to each other in the tire width direction from the outermost circumferential groove 5S. , Mn is printed.

In the inner adjacent circumferential groove trace Mn, the ridge portion 7N in the inner adjacent circumferential direction groove 5N is formed at a shallow position near the tread tread surface 6f, so that the ridge portion 7N touches the ground and the ridge portion 7N is grounded. A trace m7 where 7N is grounded is formed.

As shown in FIG. 6, in the footprint P when the tire is new, the front-rear length of the equatorial circumferential groove trace Mc and both outer side traces of the tire is the longest, and the front-rear length of the outermost circumferential groove trace Ms between them is the longest. The shortest, the anteroposterior length of the inner adjacent circumferential groove trace Mn has an intermediate length between the anteroposterior length of the equatorial circumferential groove trace Mc and the anteroposterior length of the outermost circumferential groove trace Ms, and has a butterfly shape as a whole. ing.
As the tire travels, the outer diameter of the outermost circumferential groove grows fastest, so the length of the outermost circumferential groove trace Ms increases, and the footprint becomes rectangular and averaged in the tire width direction. To do.

When the vehicle travels on a wet road surface, the front edge of the tire contact patch (corresponding to the front edge Ef of the footprint) acts to drive water forward (white arrow).
Therefore, when water is driven in front of the wavy front end edge Ef of the butterfly-shaped footprint P when the tire is new, water is most likely to collect in the left and right recesses Vs where the outermost circumferential groove trace Ms is located. In addition, water tends to collect in the front Vc of the central convex portion where the equatorial groove trace Mc is located.
If this accumulated water is not drained, the wet grip performance will be lost and a hydroplaning phenomenon will occur.

Therefore, the water in the recess Vs where the water at which the outermost circumferential groove trace Ms is located is most likely to be drained is drained by the outermost circumferential groove, so that the outermost circumferential groove is required to have high drainage.
On the other hand, since it is difficult for water to collect in the place where the inner adjacent circumferential groove trace Mn is located between the outermost circumferential groove trace Ms and the equatorial circumferential groove trace Mc, high drainage property is required for the inner adjacent circumferential groove trace. Not done.

In the pneumatic tire 1, as shown in FIG. 3, the ridge portion 7S in the outermost circumferential groove 5S located on the outermost side of the circumferential groove 5 in the tire width direction extends from the tread tread 6f to the groove bottom. Since it is formed at the intermediate depth position of the groove between the two, when the rib-shaped land portion 6 touches the ground, the opposing ridges 7S and 7S abut and support each other, and the rib-shaped land portion 6 is deformed. In addition to suppressing the increase in rolling resistance, the outer groove space 5So is formed with a sufficient volume on the outer peripheral side of the ridges 7S and 7S to provide high drainage, and the outermost circumferential groove trace Ms. The water that collects in the front can be efficiently discharged, and the wet grip performance can be ensured high.

On the other hand, as shown in FIG. 4, the ridge portion 7N in the inner adjacent circumferential groove 5N located adjacent to the innermost circumferential groove 5S in the tire width direction is between the tread tread 6f and the groove bottom. It is formed at a shallow position near the tread tread 6f of the groove, and when the ribbed land portion 6 touches the ground, the opposing ridges 7N and 7N come into contact with each other and support each other, suppressing an increase in rolling resistance and suppressing an increase in rolling resistance. Although the ridges 7N and 7N are formed at a shallow position and the drainage property is not high, it is difficult for water to collect in front of the inner adjacent circumferential groove trace Mn, so that the necessary drainage property is secured and the drainage property is closer to the tread tread. There is a high possibility that the ridges 7N and 7N formed at the shallow position of the tire will touch the ground, and the wet grip performance can be improved by expanding the ground contact area.

In the pneumatic tire 1, as shown in FIG. 2, a plurality of ridges 7N in the inner adjacent circumferential groove 5N are formed at intervals in the tread circumferential direction, so that the ridges 7N are adjacent to each other in the circumferential direction. There is a communication space between the strips 7N and 7N that communicates the outer groove space 5No and the inner groove space 5Ni, and the drainage property is improved. The water in front of the inner adjacent circumferential groove trace Mn is drained to the outermost side. It is possible to suppress the flow of water toward the circumferential groove to some extent, reduce the burden of drainage by the outermost circumferential groove, effectively share the drainage, and improve the wet grip performance as a whole. ..

Further, the ridge portion 7S in the outermost circumferential groove 5S is formed at an intermediate depth position of the groove between the tread tread surface 6f and the groove bottom, and the volume of the outer groove space 5So on the outer peripheral side of the ridge portion 7S is large. It can be secured large and maintains high drainage.
Further, as shown in FIG. 2, since the ridge portion 7S in the outermost circumferential groove 5S is continuously formed in the tread circumferential direction, the ridge portion 7S facing the rib-shaped land portion 6 when it touches the ground. , 7S are in continuous contact with each other and firmly support each other, the deformation of the rib-shaped land portion 6 can be suppressed as much as possible, and the increase in rolling resistance can be reliably suppressed.

As shown in FIG. 5, since the ridge portion 7C in the equatorial circumferential groove 5C is formed at the intermediate depth position of the groove between the tread tread surface 6f and the groove bottom, the rib-shaped land portion 6 touches the ground. When this happens, the opposing ridges 7C and 7C come into contact with each other and support each other, suppressing the deformation of the ribbed land portion 6 and suppressing the increase in rolling resistance, and the outer circumference of the ridges 7C and 7C. The outer groove space 5Co has a sufficient volume on the side and has high drainage property, efficiently drains the water accumulated in front of the equatorial circumferential groove trace Mc, and the inner adjacent circumferential groove 5N and the outermost circumferential groove 5S. It suppresses the flow of water toward the side, reduces the burden of drainage on the outermost circumferential groove 5S, effectively shares the drainage, and improves the overall wet grip performance over the entire tire width direction. be able to.

Further, as shown in FIG. 2, since the ridge portion 7C in the equatorial circumferential groove 5C is continuously formed in the tread circumferential direction, the ridge portion 7C facing the rib-shaped land portion 6 when it touches the ground. Since the 7Cs and 7Cs are in continuous contact with each other and firmly support each other, the deformation of the rib-shaped land portion 6 can be suppressed as much as possible, and the increase in rolling resistance can be reliably suppressed.

With reference to FIGS. 3 to 5, the ridge portion 7S in the outermost circumferential groove 5S and the ridge portion 7C in the equatorial circumferential groove 5C are the inner peripheral surfaces 7nb of the ridge portion 7N in the inner adjacent circumferential groove 5N. It is formed at a deeper position in the groove on the inner side in the radial direction of the tire.
That is, as described above, there is the following relationship.
Dsa (depth of outer peripheral surface 7sa of ridge 7S)> Dnb (depth of inner peripheral surface 7nb of ridge 7N)
Dca (depth of outer peripheral surface 7ca of ridge 7C)> Dnb (depth of inner peripheral surface 7nb of ridge 7N)

Therefore, until the wear of the tread tread 6f reaches the ridge portion 7N formed at a shallow position of the inner adjacent circumferential groove 5N and the ridge portion 7N is further lost, the inner adjacent circumferential grooves 5N are in contact with each other. Although it is blocked by the ridges 7N and 7N, the outer groove spaces 5So and 5Co still remain on the outer peripheral side of the ridges 7S and 7C in the outermost circumferential groove 5S and the equatorial circumferential groove 5C to maintain drainage. After the ridge portion 7N of the inner adjacent circumferential groove 5N is lost, the groove space opens in the inner adjacent circumferential groove 5N, so that the outermost circumferential groove 5S and the equatorial circumferential groove 5C are formed. Drainage can be secured even if the ridges 7S and 7S and the ridges 7C and 7C are blocked, respectively.

That is, drainage is ensured by at least one of the outermost circumferential groove 5S, the equatorial circumferential groove 5C, and the inner adjacent circumferential groove 5N from the time when the tire is new until it is completely worn, and the wet grip performance is maintained. be able to.

Further, until the ridges 7N of the inner adjacent circumferential grooves 5N are substantially lost due to wear, the ridges 7S and 7S of the outermost circumferential grooves 5S and the ridges 5C of the equatorial groove 5C are in contact with each other. In addition to the portions 7C and 7C, the remaining ridge portions 7N and 7N of the inner adjacent circumferential groove 5N ensure the rigidity of the rib-shaped land portion 6 and suppress an increase in rolling resistance.
After the ridge portion 7N of the inner adjacent circumferential groove 5N is lost, the protruding length (height) of the rib-shaped land portions 6 on both sides of the inner adjacent circumferential groove 5N from the groove bottom becomes smaller. Therefore, the rigidity of the ribbed land portion 6 is not significantly reduced, and the increase in rolling resistance is appropriately suppressed.

The pneumatic tire 1 is configured by stacking a plurality of inclined belts in which the belt layer 3 is oriented in the direction in which the cord is inclined with respect to the tire equatorial line Lc, and the belt layer 3 is formed as shown in FIG. Of the five circumferential grooves 5 extending in the tread circumferential direction in the tread 4, the outermost circumferential grooves 5S and 5S located on the outermost side in the tire width direction are within the width W of the belt layer 3 in the tire width direction. Since it is located at, the footprint P when the tire is new has a typical butterfly shape as shown in FIG.

In the pneumatic tire 1 having a typical butterfly-shaped footprint when the tire is new, the ridge portion 7S of the outermost circumferential groove 5S of the present invention is formed in the groove between the tread tread surface 6f and the groove bottom. The most suitable configuration is that the ridge portion 7N of the inner adjacent circumferential groove 5N is formed at an intermediate depth position and is formed at a shallow position closer to the tread tread surface 6f of the groove between the tread tread surface 6f and the groove bottom. Efficiently discharges the water that collects in front of the outermost circumferential groove trace Ms while suppressing the increase in rolling resistance, and improves the wet grip performance by expanding the ground contact area by the ridge 7N in the inner adjacent circumferential groove 5N. The effect of trying to achieve the above can be more remarkable.

Table 1 shows the test results of rolling resistance performance and wet grip performance of the example of the pneumatic tire having the tread structure of the present embodiment as evaluation results in comparison with the conventional examples 1 and 2.

The pneumatic tire of this embodiment has a tire size of 315 / 70R22.5, and the tread has five circumferential grooves extending in the tread width direction in the tread circumferential direction. The same ridge is formed in each of the five circumferential grooves.
The pneumatic tires of the conventional example 1 and the conventional example 2 also have the same tire size as that of the embodiment. In the conventional example 1, five circumferential grooves are extended in the tread width direction, but the tread is projected. It does not have a tread.
Conventional Example 2 is a pneumatic tire having no circumferential groove in the tread.

Table 1 shows the evaluation results of the performance tests of the rolling resistance performance and the wet grip performance of the pneumatic tires of the above-mentioned Example 1 and Conventional Examples 1 and 2.

[Table 1]

The rolling resistance test measures the rolling resistance by the force method conforming to the international standard ISO28580.
The evaluation results of the rolling resistance coefficient RRC shown in Table 1 are shown by using the reciprocal of the measured rolling resistance coefficient RRC obtained by dividing the measured value of the measured rolling resistance by the load, with an index of 100 in Conventional Example 1. ..
The larger the index value, the smaller the rolling resistance.

In the wet grip test, the wet grip is measured by the actual vehicle method conforming to the international standard ISO15222.
The evaluation result of the wet grip index shown in Table 1 shows the measured value of the measured wet grip as an index with the conventional example 1 as 100.
The larger this index value is, the better the wet grip performance is.

As shown in Table 1, Conventional Example 2 having no circumferential groove has high tread rigidity because there is no circumferential groove, and the rolling resistance coefficient RRC shows a large value of 111.1, but drainage due to the circumferential groove is shown. The wet grip index is 90.9, which is extremely small.

On the other hand, in the embodiment, since the tread has a ridge portion facing the circumferential groove, the rigidity of the tread is maintained high, the rolling resistance coefficient RRC shows a large value of 107.5, and the rolling resistance is increased. It is decreasing.
The rolling resistance coefficient RRC of this embodiment is naturally lower than that of the conventional example 2 having no circumferential groove, but shows a considerably large value.

Further, in the embodiment, the ridge portion 7S of the outermost circumferential groove 5S is formed at an intermediate depth position, and the ridge portion 7N of the inner adjacent circumferential groove 5N is formed at a shallow position near the tread tread, and the circumference of the equator. Drainage is effectively shared with appropriate drainage depending on the position of the circumferential groove in the tire width direction, such that the ridge portion 7C of the directional groove 5C is formed at an intermediate depth position. Therefore, the wet grip index shows a large value of 104.2, and the wet grip performance is also improved.

The wet grip index 104.2 of this embodiment is naturally larger than the wet grip index 90.9 of the conventional example 2 having no circumferential groove, and also has the wet grip of the conventional example 1 having five circumferential grooves having no ridges. Wet grip performance is improved with a value larger than the index 100.

This is because the conventional example 1 does not have a ridge portion in the circumferential groove, so that when the rib-shaped land portion touches the ground, the rib-shaped land portion may be compressed and deformed or collapsed, resulting in poor drainage of the circumferential groove. It is thought that this is because.

Although the tread structure of the pneumatic tire according to the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to the above embodiment, and is carried out in various embodiments within the scope of the gist of the present invention. Is included.
For example, the present invention is not limited to five circumferential grooves, and the present invention is also applied to a pneumatic tire having four or six or more circumferential grooves.
Further, although the ridge portion of the inner adjacent circumferential groove is formed at a shallow position near the tread tread, the outer peripheral surface of the ridge portion may be substantially the same surface as the tread tread.

The pneumatic tire according to the present invention has a rib pattern on the tread in which a rib-shaped land portion is formed by a circumferential groove, and the rib-shaped land portion has a sipe or the like for wet grip performance, braking on ice, or the like. Fine grooves may be formed.

1 ... Pneumatic tire, 2 ... Carcass, 3 ... Belt layer, 4 ... Tread, 5 ... Circumferential groove, 5C ... Equatorial circumferential groove, 5S ... Outermost circumferential groove, 5N ... Inner adjacent circumferential groove, 6 ... Ribbed land part, 7C, 7S, 7N ... ridge part, 8c, 8s, 8n ... groove bottom.

Claims (8)

In a pneumatic tire in which a plurality of rib-shaped land portions are formed by at least four circumferential grooves extending in the circumferential direction of the tread.
Protruding portions protruding in the direction of each other from both side wall surfaces of the rib-shaped land portions adjacent to each other across the circumferential groove are formed so as to extend in the circumferential direction of the tread.
The opposing ridges have a gap between them and the bottom of the groove, and the tip surfaces of the ridges facing each other have a gap in contact with each other due to elastic deformation of the rib-shaped land portion that touches the ground when the tire touches the ground. Arranged,
The ridge portion in the inner adjacent circumferential groove located adjacent to the innermost peripheral groove portion in the tire width direction from the outermost circumferential groove portion located on the outermost side in the tire width direction of the circumferential groove is the outermost circumferential groove. A pneumatic tire characterized in that it is formed at a shallower position closer to the tread tread of the groove between the tread tread and the groove bottom than the ridge portion. The ridge portion in the outermost circumferential groove is located at an intermediate depth of the groove between the tread tread and the groove bottom, and is on the groove bottom side of the inner peripheral surface of the ridge portion in the inner adjacent circumferential groove. The pneumatic tire according to claim 1, wherein the tire is formed at a deep position in the groove of the tire. The pneumatic tire according to claim 1 or 2, wherein a plurality of the ridges in the inner adjacent circumferential groove are formed at intervals in the tread circumferential direction. The pneumatic tire according to any one of claims 1 to 3, wherein the ridge portion in the outermost circumferential groove is continuously formed in the tread circumferential direction. The ridge portion in the equator circumferential groove located at the center of the tire width direction of the circumferential groove is formed at the intermediate depth position of the groove between the tread tread and the groove bottom. The pneumatic tire according to any one of claims 1 to 4, which is characteristic. The pneumatic tire according to claim 5, wherein the ridge portion in the equatorial circumferential groove is continuously formed in the tread circumferential direction. 5. Claim 5 or claim, wherein the ridge portion in the equatorial circumferential groove is formed at a position deep in the groove bottom side of the inner peripheral surface of the ridge portion in the inner adjacent circumferential groove. Item 6. The pneumatic tire according to item 6. The belt layer embedded in the tread portion where the circumferential groove is formed is composed of a plurality of inclined belts in which the cord is oriented in an inclined direction with respect to the tire equatorial line.
The pneumatic tire according to any one of claims 1 to 7, wherein the outermost circumferential groove is located within the width of the belt layer in the tire width direction.

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